1. Field of the Invention
The present invention is related to an installation for polymerization by ionization of structures, in particularly of substantial dimensions, constituted principally of composite materials and more precisely for irradiation by x-rays or electrons of resins used in the composition of composite materials, in particular, although not exclusively, of complex elements of revolution such as for example cylindrical enclosures or reservoirs having hemispherical or similarly shaped ends.
2. Description of Background and Material Information
It has been known for a number of years to treat elements made out of composite materials constituted by fibers, fabrics, glass felts, Kevlar, carbon and other materials, with a radio hardening resin and assembly elements and/or inserts in particular metallic or other types of materials, the said composite material being able to present a substantial thickness by subjecting this material to irradiation by electronic radiation or x-ray radiation so as to polymerize or crosslink the resin without heating.
For more details of such a technique, one may refer to European Patent publication No. 165,118 filed in name of applicant and, more particularly, adapted for the treatment of elongated elements revolution such as tubes, the disclosure of which is hereby incorporated by reference thereto.
This document describes in particular a polymerization/crosslinking installation comprising means for producing an electron beam, means for directing the electron beam towards the element to be treated, a target adapted to generate under the effect of the electron beam an X-ray radiation, means for placing the target along the trajectory of the electrons or outside thereof so as to irradiate the element respectively with X-ray radiation or with electronic radiation, respectively, and means for carrying out a relative movement between the irradiating beam and the element such that it be subjected entirely or partially to the effect of one of the said irradiations.
The relative movement in question comprises a displacement of the element along its axis, horizontally and orthogonally to the axis of the irradiating beam, combined with the rotation of the element around its axis.
Furthermore, the dosages necessary for irradiating the resin of the composite material of the element for its polymerization being a function, in the case of X-ray radiation, of the distance between the target and the element, it is envisioned to adjust this distance and, particularly, to optimize the time of polymerization.
Two embodiments are envisioned: the element is positioned in a manner so as to be brought closer or spaced from the target, or the axis of the element is maintained fixed and the target is displaced in a direction of the elements.
In the installation shown and described in Publication No. 165,118, the electron generator is fixedly mounted in its protection protective compartment, the electron gun being arranged vertically and turned towards the ground. The scanning horn of the generator traverses through a window a horizontal shield separating the said protective compartment from the subjacent irradiation cell in which the element to be irradiated is displaced, carried by an appropriate cart.
The element, an elongated tube of composite material, can pass along under the generator horn, a conversion target being interposed between this horn and the element when one wishes to irradiate the latter with X-ray radiation.
According to a second method of adjusting the distance between the target and the element, the retractable target is furthermore movably mounted along the axis of the irradiating beam.
Although such a mounting allows for a better adjustment of the irradiation dosages necessary in particular in the case of substantial thickness of composite material, and is adapted to the type of element to be treated, namely tubular elements, it nevertheless has two major disadvantages.
On the one hand, it requires a modification of the concentration of the electron beam hitting the target when the distance between it and the outlet window of the horn is modified.
Indeed, the electron beam such as geometrically defined by the outlet window of the horn is slightly divergent such that a spacing of the target causes a correlational reduction in the concentration of the electron beam on the target and thus of the intensity of the X-ray radiation generated.
To overcome this, one could dimension the target accordingly, but the increase in the surface of the target would rapidly reach its limits, on the one hand, geometrically, and on the other hand, mechanically, because problems of cooling and retaining the target which is a thin plate subjected on its internal surface to a cooling and a strong vacuum occur.
As a result, one cannot allow for a large back and forth movement of the target around its optimum position with respect to the horn, without utilizing an overly powerful electron accelerator, which is also not satisfactory.
The requirement for correcting the correlational concentration of the electron beam leaving the horn thus renders more complex and delicate the management of the control means of the irradiation apparatus.
Furthermore, the practical limits of the displacement of the target relative to the horn considerably reduce the capacity of the irradiation apparatus.
If the latter can be appropriate to treat the tubular elements of the type shown in the document cited above whose composite portions are positioned in a fork of a distance with respect to the horn which is relatively narrow, it is also true, that from one element to another, it is necessary to modify or adjust the mounting system on the movable cart to correctly position the composite portions spaced with respect to the horn which is fixed. The irradiation apparatus cannot treat elements whose geometry is such that the portions of composite material are positioned in a range of spacing with respect to the axis of the element which is very substantial, which is for example the case with the rounded/curved, hemispherical or otherwise, end portions of the enclosures or reservoirs described above.
Of course, in such a case the difficulty can be overcome by providing, in addition to the mobility of the target with respect to the element, a mobility, along the axis of the irradiation beam, of the element on its transport cart.
Unfortunately, such a solution makes the control of the irradiation installation yet more complex, costly and delicate because, in addition, it is necessary to design special transport carts and to control them accordingly with respect to the spacing of the element with respect to the electron generator.